Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1780155 | New Astronomy Reviews | 2008 | 4 Pages |
Our physical intuition usually separates space from time, ignoring the spacetime character of the physical reality. In strongly curved spacetimes this may lead to confusion and paradoxes. I present here two examples: (1) in the non-static cosmological spacetimes with flat space sections, the cosmological expansion of space is a true physical effect. Contrary to what the intuition imagines, it cannot be explained as a motion of matter in a non-expanding flat space. (2) Contrary to intuition, for static spacetimes the mathematically simplest 3+13+1 split is not given by the direct projection as in the standard ADM scheme. The simplest split is defined by a counter intuitive “optical geometry” that redshifts both space and time by the same conformal factor.